Various types of electronic equipment, for instance, information equipment, AV equipment, and game machines, have an input member such as a push-button switch which determines the on/off state of a switch in response to pressing of a push-button. The push-button switch to be used has a configuration in which a key sheet having a push-button (key top) overlies a circuit board on which a contact switch is disposed. The push-button switch with such a configuration often has an illumination function to illuminate the key top of the key sheet with an internal light source disposed on the circuit board, thereby enabling easy operation even in a dark place.
The input by the push-button switch has been diversified with the development of various types of electronic equipment. In addition to pressing input for the binary input of the on/off state, a slide input is demanded to input coordinates by actions such as a sweep and touch. For example, Japanese Unexamined Patent Application Publication No. 2008-139961 (Patent Literature 1) discloses an input device including a sensor-integrated illuminated key sheet 111 which has a key member 112, a light guide panel 113, a pressing sheet 114, and a coordinate-inputting unit 115 as illustrated in FIG. 18. In this input device, a metallic dome functions as a contact switch for the pressing input, and the coordinate-inputting unit 115 serves for the slide input. The coordinate-inputting 115 has a structure in which a substrate 115a is disposed between a first electrode 115b and a second electrode 115c. In terms of the illumination, air spaces 116 are formed to the surface side of the light guide panel 113 to sufficiently secure the optical waveguide characteristics of the light guide panel 113, thereby enhancing the brightness of the key member 112.